This invention relates generally to fluid processing, and specifically to magnetic flowmeters for measuring process flow. In particular, the invention concerns an electrode assembly for magnetic flowmeters subject to high process pressure.
Flow sensors provide utility across a wide range of fluid processing applications, including agriculture, environmental control, water and air distribution, food and beverage preparation, bulk fluid storage and transport, chemical and pharmaceutical production, energy and hydrocarbon fuel production, and manufacturing processes utilizing thermoplastics, glues, resins and other fluidic materials. In each of these applications, the most appropriate flow measurement techniques depend not only upon the properties of the process fluid itself, but also upon the particular flow processes applied to it.
Standard flow measurement technologies include turbine flowmeters, which characterize flow as a function of mechanical rotation, and differential pressure-based devices, which characterize flow as a function of a pressure drop across an orifice plate or other differential pressure generating element, where the pressure drop is related to Bernoulli's principle and other velocity-dependent effects. Pilot tubes are also widely used, and based on similar principles. Additional technologies include mass flowmeters, which characterize flow as a function of thermal conductivity, vortex-shedding flowmeters, which characterize flow separation across a bluff body, and Coriolis flowmeters, which characterize flow as a function of momentum-dependent vibrational measurements.
Magnetic flowmeters distinguish from these technologies by measuring flow as a function of Faraday's Law, which depends upon electromagnetic rather than mechanical or thermodynamic effects. In particular, magnetic flowmeters measure flow as a function of the electromotive force induced when a magnetic field is generated across a conducting process fluid flow.
Magnetic flowmeters thus provide advantages in “dirty” and abrasive or corrosive flows, which are often unsuitable for mechanical turbines and traditional sensor probe configurations, and when differential pressure-based devices produce an unacceptable pressure drop. Because magnetic flow measurements depend upon electromagnetic induction, however, the technology also poses a number of design challenges. In particular, the flow must be conductive for the Faraday effect to occur, and the electrode assembly must be carefully insulated and sealed in order to prevent shorts and leaks. This is particularly true when the flowmeter is subject to high process pressures, for example in hydraulic fracturing and related methods of hydrocarbon fuel extraction and processing.